Memory of a Cyclic Multiphase Flow in a Porous Medium

One potential method for reactive mitigation of climate change is carbon sequestration, which involves the cyclic injection of CO2 into saline aquifers for removal from the atmosphere. Studies of memory formed by cyclic multiphase flow can possibly inform and improve the efficiency of this type of carbon sequestration. In this work, we focus on memory in the triple phase boundary of a wetted porous medium, also referred to as the contact line. We cyclically inject and withdraw a constant training volume of deionized water from a porous medium made of glass beads. The cyclic driving procedure eventually relaxes the contact line to a steady state shape. Afterwards, we drive the contact line with volume amplitudes that are less than the training volume, and we observe that the smaller amplitudes alter the contact line away from its steady state shape while the training amplitude restores it. This behavior resembles the phenomenon of return point memory, better known in ferromagnets. We propose further experiments to characterize this memory, including its capacity to retain traces of multiple driving amplitudes.